Probing the Interlayer Exciton Physics in a MoS₂/MoSe₂/MoS₂ van der Waals Heterostructure

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Engineering properties of semiconducting transition metal dichalcogenides (TMDs) via atomic monolayer stacking is a key strategy.
• Staggered band alignment in TMD heterostructures theoretically enables long-lived interlayer excitons and robust valley polarization.
• Simultaneous observation of these features has been limited, primarily to MoSe₂/WSe₂ heterostructures.

Purpose of the Study:

• To report the observation of long-lived interlayer exciton emission in a MoS₂/MoSe₂/MoS₂ trilayer van der Waals heterostructure.
• To confirm the interlayer nature of the transition and investigate its properties.
• To explore the potential for controlling valley polarization in TMD heterostructures.

Main Methods:

• Photoluminescence spectroscopy was employed to confirm the interlayer nature of the observed transition.
• Analysis of temporal, excitation power, and temperature dependence of the interlayer emission peak.
• Circularly polarized optical pumping was used to investigate valley polarization dynamics.

Main Results:

• Long-lived interlayer exciton emission was observed in a MoS₂/MoSe₂/MoS₂ trilayer.
• Complex photoluminescence dynamics suggest quasi-degenerate momentum-direct and momentum-indirect bandgaps.
• Circularly polarized optical pumping induced long-lived valley polarization of interlayer excitons with opposite helicity to the excitation.

Conclusions:

• The study successfully demonstrates long-lived interlayer exciton emission in a MoS₂/MoSe₂/MoS₂ trilayer.
• The results confirm that careful selection of TMDs in van der Waals heterostructures allows for control over the circular polarization of interlayer exciton emission.
• This provides a pathway for designing novel optoelectronic devices with tailored polarization properties.